Progressive die and method of making it



March 22, 1949. A. D. JOHNSON v 2,465,019

y PROGRESSIVE DIA-E ANDMETHOD OF MAKING IT Filed Jan. 2, .1946 4 2 shee'ts-sneet 1 ATTORNEY March 22 1949. A. D. JoHNsoN PROGRESSIVE DIE AND METHOD OF MAKING IT 2 Sheets-.Sheet Filed Jan. 2, 1946 INVENToR. ARTHUR D. JOHNSON ATTORNEY yPatented Mar. 22, 1949 *A UNITED fs EBASrENr o Eric-c @msnm-9 l PROGRESSIVE: DIE ANDaME'lEHOD 0F *.MAKINGJT 'Arthur-D. Johnson,y Poway,`Calif., assignor'to "Solar #Aircraftf' Company, San Diego; Calif., `a -tcorporation o"alifornia ApplicationJanuary v2, 1946, Serial No. 638,618 `realm (or-.225195) v1 2 This invention relatestotheidie stamping of Referring to the drawing: Y' sheet metal strips' by the process .in which"'the ,'Fig. lis 4a. perspective view showing-,apdiepress strip to be formed is intermittently 'fedlongicontaininga pair of complementary,V progressive 1i tudinally between what are knownas progressive dies =for the forming of.,.a Ysheet y metal strip;

forming dies, the dies being brought togtherlto t5 Iig. 2ris a plan view'of the lower-die illustrated 'shape longitudinally successive portions of the .in .thepress of:fFig. l;

"strip between the intermittent movementspthere- Eig 3is..a cross-section of the. die. showing theof, so that when the strip has .passed `completely ccontour of the, latter in the. planes `III--IIIrof through the die it is of 'uniform cross-sectional J:Fig..2 and atalllongitudinalpoints therebetween;

contour from end to end. ""10 `Fig..4 is across-section showing the contourof An object-oi theinvention is to provide pro- ',.theidiein the plane IV-IVof kF.ig..2; gressive dies, the cross-sectional contourofwhch l"F.ig.,-5 is a cross-section showing the-,contour `varies in such manner( from. endv toferidfthereof A* of the, dieiinfthe plane V-.Voi Fig. 2; that the sheet formed' by; thedies isgradually r`liig. 6, is vva longitudinal. sectionthrough astartworked into the desired shape with...rela'tively "MingDatternshowing.the initialstage in the prepalittle local thinningjthickening, or Wrinkling. .ration ,of the'die of Fig. 2;

Another object is to `enable relatively unskilled Fig. '7..is aview-v similar toiFigfG, but, showing workmen tov make progressive dies of ,desirably a secondstage in the. process; varying cross-sectional contou'rfrom end .to end. Fis.` 8 is a viewsimilar to Fig. 7, showing ya third ther more specic objects and'features oithe @onstage .in the process; invention Will appear from the detailed..descrip Fig. H9:15 ,a View Similar 170 Fg- 3, ShOWIlfa tion to follow of my dies and the method of m'akfourth Stage ih theDrOCeSS; ing them. 1.' Eig.;l 10lis aviewsimilar to-lig.l 9, butshowing Heretofore; progressive dies havebeenmadegby aith Stage ih the PIOCESS; and

for the dies by hand,l so as togobtain asmoth ,plastenpattern.corresponding tof-the die 0f Eig.

and gradual variation ofthecross-sectional con- 2,the section beingvtaken nthevvplane XI-VXI tour from end to end ofA the'dies. "That method ,fof` Fig.' 2. is relatively expensive because highly skilledartl-v Referring ,ii-rst toiFig.f.1,there is showna, con- `sans are required-for'the shaping. operatirln;y and 30iventional-.sheet metal .stampingpress l5. conoft times the dies-'must be repeatedly formedarld Itaining a lower stationary die I6 andfan upper Atested. before'a'shape is arrived at"thatproduces movableidie Il. The stationarydie I6v isshown satisfactory'results. restingona bedk l'8,of the press, Whereasgthe up- In accordance with the-present"inventionprol yperwdie' l1. vis secured to the .movable .platenalof gressive dies having desirable" shape canbegpro- ,35 .`the,press,,sov that. it cansbemoved towarda-nd duced relativelyquickly and'byaro'utne procev4away fromthestationarydiel I6.to `forma metal ydure capable of being'practicedbyrelatively, un- .stripA 20 .ast the vlattergisf fed longitudinallyabe.. skilled workmen. Briefly; the processcomp'rises .;tweenthedies between-successivastampingopyirst forming a pattern of uniform crossesecton'al zerations.

contour throughout, corresponding tojthe contour 4.0 ...IReferrng'toFigs 2te 5, inclusive, it jwill bey ob- 'of the finished strip to be formed. There' is then :served `that the vlower die. I6. is curvedlongitudibuilt up on this pattern a relatively s thin and 'nallycimboththehorizontal land .the -vertical exible but substantially non-stretchable pattern. planes .and f that r`its CIOSSfSeCtiOnal .contour 'The thin 'flexiblepatterm:having the; coniigura- -fvaries longitudinally. ,Thus at .-thelower, or front vtion ofthe vsheetsfto'be formed-is 'thengdistorted `-45 end of thediev (as viewed inlFig. 2)@the-working by hand so thatit-"gradually varies from the orgi face of s the, die is at .as indicated. in Eig; 5,.:but nal contour at one end to asimpler contouratl'the Yin the planesIII-III and at all pointstherbeother end. The re shaped thin'exiblepattern ltween, cit :has-,a curved contour as shown in liig. is then used as a mold to forma pattern of plaster I3. Thus, the die r,has rather short and :deep or the like, whichplasterpattern can Lthenlbe 50 grooves 2| and 22 near its side edges, -Athese used in accordance with'. well-.'knownpracticegto grooves being of irregularshape,V and has afhigh form' a metal die. 'After producing oneldie 0r.,die ,gradual rise 23,in the center. The cross-sectionpattern in the ymanner described, amcomplemen- Walshapeshown \.inFig.3icorrespondsuexactlyito tary.Y die-can beprepared from itin vaccordance that/of.. thenished strip. to betformedebetween with known'practices. 55 'the dies.

The cross-sectional shape of the die varies gradually from the flat shape at the front end as illustrated in Fig. 5, to the plane III-III. Thus, by observing Fig. 4, it will be observed that while the contour is approximately the same as that shown in Fig. 3, the grooves 2| and 22 are much shallower and the rise 23 is not as high.

A pattern identical in shape with the die shown in Fig. 2, can be prepared in accordance with the invention by the following steps:

Referring first to Fig. 6, a plaster pattern 24 having an upper face corresponding in contour to the nished sheet is prepared. In other words, Y

this pattern 24 has a contour throughout its length corresponding to that shown in Fig. 3.'

many known procedures which do not constitute a part of the present invention.

As the initial step in the preparation of a progressive die from the pattern 24, a sheet pattern 25 is built up on that longitudinal section of the pattern 24 corresponding to the longitudinal portion extending from the front end to the first plane III- III of Fig. 2, the plane in which Fig. 6 is taken corresponding to the plane XI-XI of Fig. 2. This sheet pattern .25 may consist of wax reinforced with. cheesecloth and may be formed by a process set forth in detail in Patent No. 2,383,706, issued August 28, 1945, on Method of making preliminary shaping die. Briefly, it involves the steps of rst brushing a coat of liquid wax on the pattern 24; second, pressing a sheet of cheesecloth into the surface of the wax; third, brushing a second coat of melted wax on top of the cheesecloth; fourth, laying a second sheet of cheesecloth on top of the second layer of wax and pressing it into the wax; and fifth, brushing another coat of melted Wax on top of the second sheet of cheesecloth. The second sheet of cheesecloth is preferably laid on the bias with respect to the first sheet so that the warp and weft threads of the cheesecloth in the two sheets are effective as reinforcement to prevent stretching of the sheet in substantially all directions.

Prior to the building up of the sheet pattern 25, a row of nails 26 may be laid points up on the pattern 24 in a line extending across the pattern so that when the pattern has been formed the nails are anchored therein with their points projecting beyond the upper surface of the sheet *pattern 25.

Referring to Fig. 7, a layer of plaster 21 is built up on the left end of the pattern 24 and overlapped onto the sheet pattern 25 and the nails 26, so that when the layer 21 of plaster has hardened, it is anchored to the end of the sheet pattern 25 by nails 26. The layer of plaster I21 is preferably substantially thicker than the sheet pattern 25 and has an edge 28 of appreciable width at its line of joinder to the sheet pattern. A row of nails 29 is driven into this edge 2B while the plaster is still soft, as illustrated in Fig. 8.

After the plaster layer 21 has hardened, the unit consisting of it and the sheet pattern 25 is removed from the pattern 24 and flexibly supported for shaping. As shown in Fig. 8, the unit is supported upon holsters 30 of clay or the like, which bolsters can be re-shaped or changed as necessary to provide the necessary support at the desired points.

The sheet pattern 25 is next shaped by bending it with the hands to gradually flatten it from its left end where it is joined to the plaster layer 21 to its right end. This change in the configuofp1aster, as shown in Fig. 9. This layer 3i is of substantially the same thickness as the layer 21, and the two layers are bound together by the reinforcing nails 29.

After the plaster layer 3i has hardened, the entire unit is inverted as shown in Fig. 10, and supported on bolsters 32 of number and size sufiicient to prevent deformation of the unit. Side walls 33 are then built up along the edges of the unit to define therewith a mold box into which plaster may be poured. When the plaster has set, it is removed from the box and inverted as shown in Fig. 11. It constitutes a plaster pattern 34 identical in shape with the die I6 of Fig. 2, and can be used to form a mold in which to cast the die I6 of Fig. 2.

It is to be understood that it is not essential to make the sheet 25 shorter than the starting pattern 24 and fill out with the layer of plaster 21, as has been described. It is often found desirable in practice to form that portion of the pattern that is not to be attened by means of the plaster layer 21. However, it will be apparent to those skilled in the art that if desired, the sheet pattern 25 can be formed over the whole length of the starting pattern 24 if care is taken in handling not to distort that portion of the sheet pattern 25 that is to be reproduced in its original form.

It will be observed that the entire process beginning with the formation of the sheet pattern in 25 and ending with the finished pattern 34 of Fig. 1l, involves only routine operations which do not require any special skill for their proper performance. Furthermore, the process inherently yields a progressive die in which the actual width of the working face of the die is the same in all cross-sectional planes thereof, which means that the sheet metal that is formed in the resultant dies will be shaped substantially by pure bending operations with no compression or stretching of the sheet.

Although for the purpose of explaining the invention, the procedure in accordance therewith has been described in detail, it will be apparent to those skilled in the art that numerous varia- -tions from the exact procedure described can be made without departing from the invention which is to be limited only to the extent set forth in the appended claim.

I claim:

The method of making a progressive die, having a working face the transverse contour of which progressively varies longitudinally of the die, from a starting pattern having the same transverse contour throughout as the desired article to be produced by the progressive die, said method comprising the steps of: first, forming on said starting pattern a flexible sheet pattern of substantial length relative to its width into a shape the transverse contour of which is the same throughout and the `same as the said article; second, reinforcing a section of said sheet pattern with a coating of time-setting plaster material on one face thereof to form a section that is non-stretchable and non-compressible; third, removing said sheet pattern from said starting pattern and progressively flattening and Widening it between successive longitudinal points thereon beyond the section that has been made noncompressible, to gradually reduce its depth and increase its projected width Without materially changing its width along its transverse contour and without changing its length; fourth, reinforcing said sheet pattern with a coating of time-setting plastic material on one face thereof; and fifth, using Said progressively attened sheet pattern as a mold to reproduce its shape in the lprogressive die to be made.

ARTHUR D. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

